From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794046784; b=km5a6x4sLNQHO3drePusyTjxyvP4UKrmyd8WuEvWhYfh1BWh8hsQohIHD4/cu/X8X25V FR+FYUUwFGvWFO7SZ+ODdRuzv/Luw+0lHiOh2h5otu1Sh27xmjEY6VY5HPdww4yqx9Zt6 M/5cy7LxhErBGPXGakHxZpF3UftsR3m9uGiHXOXI687GYE+kxG/9PpLMakJOjZDhFyyOf cK3bYSrJeV1WQJ1+fPUdXme2Ja5W7lNhcVl7P0uYzZBP7gz4K5ShrNNCtZg5lTIMG6Lu9 M5wsiNPQEWTYWZBu0pn4P8O9nq1wKPZvbY0mtRBw5+Pm/twMCUu4MeYzfWxFKw2VN2A== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794046784; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: MIME-Version:Content-Type:Content-Transfer-Encoding; bh=QpBFjVgElnaHzeHQS+r6f9rKajllvimEeA195p1NErA=; b=qTRdqRO3pZpyr1KD6L/qMYrN3giMCmlZXsnNIxBNOzkIP9zAyN4obpxiakAGOiKeh3ts MD7FLL6lS80wfkDMonjFr7oZopcCbf5JnoztKus6IZCoKalNSWKl4aXMYWBweWp3jlTPK Kc/ILxrDm+9CaZi5NZDtaajJR9iDl/ncUQj+nfVjRltYq+i2iHz3X4JyJga/mv4FEotuD WiJ4K89Ltj9yWFstJWaqwr2WI3y/yd+8uSejS3h2qVmrWbnzbEBvveT5koVfrk4/AwWV9 2sqZaFpqy+vpUtw2v05oxeaoSKU6tDS9QMocnzthYDcM4kvq2BHxJhAPzoW2z+rtnag== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=R9fX3bEe; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id EE021606EEBE for ; Sat, 7 Nov 2026 10:19:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=R9fX3bEe Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5138C1F008A1; Sat, 7 Nov 2026 10:19:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794046783; bh=QpBFjVgElnaHzeHQS+r6f9rKajllvimEeA195p1NErA=; h=From:To:Cc:Subject:Date; b=R9fX3bEerU8vl75WO7sO8/f2sn/5XpzQj5Kt0AgLstiFZAcUL4Rd9XOsDKQZzSwW5 8N8g+IuJvNfzYm1DO2Ig5kd7o0A2lWEVMpFiihvxWz43c4Xfp/LYmA9wlvTaq3fjM1 20RDvEg8aXE8pOmwTiKTOyGdb8T5CoizqBCvpcSO9WgYsrk4ae38BYj9UQzTNhBYRx S8TpQgXoaE3ke6rO0eAZ+VG97YbXOEmLGRxMMIVcX09K0F1CubqeSQusBSX2Eqt3Oa FYlOzI1C8scFky9tk7DyTwt27JCKTl+Mq569U0dj1oK9cj5mocHIbXdajeg5LAifsE xYXiEBBYC+5lw== From: Sasha Levin To: sj@kernel.org, akpm@linux-foundation.org, usamaarif642@gmail.com Cc: stable@vger.kernel.org Subject: FAILED: patch "[PATCH] mm/damon/core: skip applying scheme if region split for quota fails" failed to apply to 6.12-stable tree Date: Sat, 7 Nov 2026 05:19:42 -0500 Message-ID: <20261107051942-failed-6.12-90c2fa6adfed@kernel.org> X-Mailer: git-send-email 2.53.0 X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The patch below does not apply to the 6.12-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.12.y git checkout FETCH_HEAD git cherry-pick -x 90c2fa6adfed7abe0935506a43cdff3a05c1fff0 # git commit -s git send-email --to '' --in-reply-to '20261107051942-failed-6.12-90c2fa6adfed@kernel.org' --subject-prefix 'PATCH 6.12.y' 'HEAD^..' Thanks, Sasha ------------------ original commit in Linus's tree ------------------ >From 90c2fa6adfed7abe0935506a43cdff3a05c1fff0 Mon Sep 17 00:00:00 2001 From: SJ Park Date: Tue, 1 Sep 2026 06:18:42 -0700 Subject: [PATCH] mm/damon/core: skip applying scheme if region split for quota fails Patch series "mm/damon: fix DAMOS bugs in core, paddr and vaddr". Fix misc bugs of DAMOS. Patch 1 makes DAMOS less stress memory allocator under extreme situation. Patches 2 and 3 fix wrong folios walking in DAMON_PADDR. Patches 4 and 5 fix wrong folios walking in DAMON_VADDR. Patches 6-8 handle extreme and unlikely memory situations that can cause divide by zero and underflow. All bugs are discovered by Sashiko. This patch (of 8): damos_apply_scheme() splits a region and apply the action to the subregion if it is needed for not violating the quota. The split operation (damon_split_region_at()) could fail for allocation failure. In the case, the quota could be violated. From the user's perspective, DAMOS becomes more aggressive than expected under the extreme situation. Handle the failure. The user impact is not critical. The failure of damon_split_region_at() is unlikely since it is arguably too small to fail. Also DAMOS being aggressive is limited to the single region. Users can set min_nr_regions to set the maximum size of each region. If it is reasonably set, the transient overhead shouldn't be critical. The issue was discovered [1] by Sashiko. Link: https://lore.kernel.org/20260901131850.98037-1-sj@kernel.org Link: https://lore.kernel.org/20260901131850.98037-2-sj@kernel.org Link: https://lore.kernel.org/20260718171523.87547-1-sj@kernel.org [1] Fixes: 2b8a248d5873 ("mm/damon/schemes: implement size quota for schemes application speed control") Signed-off-by: SJ Park Signed-off-by: Andrew Morton Cc: Usama Arif Cc: # 5.16.x --- mm/damon/core.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/mm/damon/core.c b/mm/damon/core.c index d63d4c6fd3ffd..53952d16ebd88 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -2607,7 +2607,8 @@ static void damos_apply_scheme(struct damon_ctx *c, struct damon_target *t, c->min_region_sz); if (!sz) goto update_stat; - damon_split_region_at(t, r, sz); + if (damon_split_region_at(t, r, sz)) + goto update_stat; } if (damos_core_filter_out(c, t, r, s)) return; -- 2.53.0